Ye Vagabonds release their second album for Rough Trade's River Lea label. Nine Waves was recorded in the Dublin Mountains at Hellfire Studios, produced by John 'Spud' Murphy (whose previous work includes records by black midi, Lankum and caroline). The album features 11 tracks of both traditional and original songs and tunes. Nine Waves follows the duo's standalone single I'm A Rover, which won them an RTE Radio One Folk Award for Best Traditional Folk Track. Ye Vagabonds were also named Best Folk Group for the second time at the 2021 ceremony, where they hold the record for most awarded artists.

The brotherly harmonies and multi-instrumental abilities of Diarmuid and Brían Mac Gloinn were joined on Nine Waves by Kate Ellis (cello) and Caimin Gilmore (double bass), both members of the Irish contemporary classical group Crash Ensemble, and Ryan Hargadon (Anna Mieke, Rachael Lavelle, Kojaque) on piano and saxophone.

The record also features concertina from Cormac Begley and harmonium from regular touring member of Ye Vagabonds, Alain McFadden.